1. Field of the Invention
The present invention relates to a display device and a method of manufacturing the same, and more particularly, to a display device which prevents a parasitic capacitance caused by a metal substrate, and a method of manufacturing the same.
2. Discussion of the Related Art
In general, a thin film transistor (hereinafter, referred to as “TFT”) is used for an active matrix type flat panel display. The active matrix type flat panel display includes a plurality of pixels defined by a plurality of gate and data lines crossing each other on a substrate. Each pixel is supplied with an electric signal by the TFT connected to the gate and data lines. Examples of the flat panel display including the TFT are liquid crystal display (LCD) device, organic light-emitting diode (OLED) and electrophoretic display.
FIG. 1 is a cross section diagram illustrating a TFT array substrate of a flat panel display according to the related art. Referring to FIG. 1, the TFT array substrate includes a plurality of pixels formed on a substrate 1. Each pixel is defined by gate and data lines (not shown) crossing each other, wherein each pixel includes a thin film transistor TFT, a pixel electrode 13 and a storage capacitor Cst. In response to a gate voltage from the gate line, the thin film transistor TFT makes the pixel electrode 13 charged with a data voltage from the data line. The data voltage charged in the pixel electrode 13 is maintained by the storage capacitor Cst.
The thin film transistor TFT includes a gate electrode 3 connected to the gate line; a source electrode 9 connected to the data line; a drain electrode 10 connected to the pixel electrode 13; and a semiconductor pattern 9 being ohmic contact with the source and drain electrodes 9 and 10. The semiconductor pattern 8 is comprised of an active layer 6 and an ohmic contact layer 7. The active layer 6 overlaps with the gate electrode 3 in state of interposing a gate insulation film 5 therebetween, wherein the active layer 6 is exposed between the source and drain electrodes 9 and 10, to thereby form a semiconductor channel. Also, the ohmic contact layer 7 overlaps between the source electrode 9 and the active layer 6, and between the drain electrode 10 and the active layer 6, so that the source and drain electrodes 9 and 10 are ohmic contact with the active layer 6. The thin film transistor TFT is protected by a protective film 11. The protective film 11 includes a contact hole 12 for exposing the drain electrode 10. Through the contact hole 12, the pixel electrode 13 is connected to the drain electrode 10.
The storage capacitor Cst is comprised of the pixel electrode 13 which overlaps with a storage line 4 in state of interposing the gate insulation film 5 and the protective film 11 therebetween.
As mentioned above, the substrate 1 for supporting the pixel array is generally made of glass. The glass has poor durability and has limitation in thinness. In this respect, the substrate of glass may cause limitation to thin profile of display device. Recently, the substrate is formed of metal which has good durability and is easy to realize the thin profile. The metal substrate 1 can realize a flexible display device which maintains a display function even in case of where the display device is bent. Also, since the metal substrate 1 is a conductor, a substrate insulation film 2 is formed on an entire surface of the metal substrate 1, so that the metal substrate 1 is insulated from the pixel array. However, there are parasitic capacitances C1 and C2 generated between the metal substrate 1 and signal lines 3 and 4 on the substrate insulation film 2. The parasitic capacitances C1 and C2 may distort the data voltage.